The present invention relates to a filter apparatus for a magnetron, and more particularly to a structure of an impedance device of the filter.
The filter is used to block a leakage electromagnetic wave from the magnetron in order to prevent the leakage electromagnetic wave from disturbing an external electronic apparatus. Particularly, an electromagnetic wave which leaks externally through a current supply line extending from a cathode of the magnetron to a power supply causes a serious problem. A filter for the leakage electromagnetic wave from the cathode line usually comprises a choke coil and a feed-through type capacitor, which is designed to exhibit a high impedance to a frequency of the leakage electromagnetic wave and inserted in the cathode line circuit.
An example of such filter is shown in Japanese patent application No. JP-A-60-243941 filed by Hitachi, Ltd. on May 18, 1984.
The prior art filter uses the expensive feed-through type capacitor as the impedance element and hence raises a problem in a manufacturing cost. Accordingly, it is desined to develop a filter which is of simpler structure and positively blocks the leakage of the electromagnetic wave.